The stripping of paint and varnish from various substrates, such as metal and/or wood, to enable the article or surface to be refinished has employed methylene chloride (dichloromethane) as the base solvent for a large variety of formulations for stripping paint and varnishes, both under industrial as well as home use. The normal additives, depending upon the degree of stability, shelf life, required have been caustic soda, ammonia, other amines, acetic acid as activators, petroleum sulfonates and other surface active materials have been added to assist in penetrating the film forming materials of the paints and varnishes. Water has been added to the point of saturating the formulation and the surface active materials of course assist in maintaining the water associated with the formulation dissolved, preventing it from phasing out. Most formulations contain a wax or similar material which is added to reduce the evaporation rate of the methylene chloride. Some formulations add a polar solvent such as methanol which the literature reports as an aid to reducing the stripping time.
The literature is filled with compositions and formulations which are purported to be substitutes for the methylene chloride based paint and varnish strippers a few of which have and still today serve a segment of industry. For example, the water based caustic formulated strippers as well as the hydrocarbon/caustic thickened compositions find utility in certain applications where to date the evaporative rate of the methylene chloride based strippers is too rapid for use, e.g. stripping of large or complex surfaces in the outdoor atmosphere. Each formulation has an advantage in some special industrial arena or work situs. However, the most universal base for strippers is still the methylene chloride/wax mixture where large vats may be filled and the article to be stripped of its coating is merely immersed into the liquid solvent formulation with or without agitation and remains in the bath for a predetermined time interval. Upon withdrawal of the article it is washed with water and/or brushed, wiped and/or flushed with water and/or fresh formulation. Since the use of large vats offers a large surface to the ambient atmosphere large quantities of the methylene chloride and/or the co-solvent such as methanol are lost. Even with the addition of the waxes the rate of evaporation is quite high. While methylene chloride is considered to be environmentally acceptable today, health problems could occur from overexposure. The American Council of Governmental and Industrial Hygienists (ACGIH) threshold limit values--time weighted average concentration for a normal 8 hour work day and a 40 hour work week, to which all workers may be repeatedly exposed, day after day, without adverse effect--for methylene chloride is 100 ppm. It would be most desirable from the human health standpoint to provide additives which would at least reduce the potential for greater exposure and most desirable to provide additives which would reduce the vapor potential to a considerable value less than the standard.
These and other advantages, will become apparent to those skilled in the art to which the invention pertains from the following description and examples.